Originally Posted by branco

Pneumatic conveying of bituminous coal and sewage sludge

Hi,

Anyone have experience in pneumatic conveying of sticky material such as cold pre-dried bituminous coal or sewage sludge with <50%DS? Thnx in adv.

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Greetings and salutations from my corner of the slowly defrosting eastern wilderness @1140 feet above mean sea level ,

Sorry to unplug your blower but:

Friction, gravity and dust explosions are the issue here.

The problem with trying to move anything that has a tendency to stick is the materials ability to adhere to itself and then the resulting plugging problem-no different than a plugged drain with grease. It is no different than blowing silage into a silo if its too wet even for high moisture hay silage.

Soft coal and its dust is a magnet for static electricity and so its not a good idea or suggestion as it would invite a spontaneous combustion fire/explosion

That is why the MSHA folks are so diligent about fining mine operators who do not clean up coal dust accumulations in underground operations

Another even better example; is why soft coal burned in a pulverized coal power plant has a physical gap between the drop zone above the paddle fans blowing the coal dust into the boiler inlet corners.

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Sewage sludge is very dense and would not be uniform in size unless it is compacted and dried and it still has the problem of residual fat and greases in it -(and by the time you have it dry enough it is ready to burn) which would adhere to the blower piping.

lzaharis ■

Greetings and salutations branco,

I used to follow the water works business with a passion subscribing to water and waste digest many years ago and I am very familiar as a lay person with potable water treatment and sewage treatment with combined sewerage and sanitary sewers

about the sludge and coal fines.

Unfortunately with those two items you are very limited.

Over here on this side of the Pacific pond the sludge in the newer sewage treatment plants the sludge either comes off a vacuum filter or filter press after the anaerobic digestion and falls into a truck mounted wheely bin- referred to as a roll off container.

Many small municipalities on this side of the Pacific Pond still use aerobic digestion and sludge drying beds due to their ease of use and low BOD

Are you using aerobic digestion with basins or an oxidation ditch with sludge drying beds?

If you are pulling out sludge with <50% dissolved solids I would want a vacuum filter in my stable (even a small one) to reduce the water load even more and recirculate the the grey water.

But if that is not an option

a screw will work but cleaning will be an issue- using a "Steam Jenny" steam cleaner works very well for grease sludge but using the liner material -see below under the open screw is a great way to solve the problem before you commission the screw.

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About the coal fines

I cannot stress the earth grounding the method of conveying enough due to static electricity and lightning. Using the national fire underwriters/fire marshals guidelines and MSHA guidelines for grounding machinery and or and using belt scrapers to clean the belts of build up are a must.

The problem with screws for coal fines is the rubbing and any fines left in the trough if the screw is not emptied completely. The grounding issue applies equally to screws for coal.

lining the trough with poly liner material such as is offered by northwest plastics from the states here is an easy way to solve the buildup problem with sludge and coal ( 011-406-293-3097 ) very slippery and no sticking as I used it to line waste salt chutes with and the stuff works.

leon ■

Search the forums for a similar issue concerning sewage sludge getting stuck in the bends & being scoured out by the drive air. The topic concerned a retrofit. ■